The subject matter described herein relates to surface inspection, and more particularly to illumination energy management in surface inspection.
As design rules and process windows continue to shrink, integrated circuit (IC) manufacturers face challenges in achieving and maintaining yields and profitability while moving to new processes. The challenges have become more difficult because inspection systems are required to capture a wider range of physical defects on wafer surfaces. One such inspection system includes the use of lasers, which provide high sensitivity to detect small defects, and a relatively high throughput.
Lasers can cause surface damage to a semiconductor wafer, e.g., from thermal shock from the laser during a surface inspection process. In some inspection systems the wafer rotates about a central axis during the inspection process. Hence, the wafer surface near the central axis moves at a slower velocity than the wafer surface near the outer edge of the wafer. Accordingly, damage tends to occur near radial inner portions of a wafer surface because relatively more energy/mm2 is imparted to the inner surface.